Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative impact of ASC 606 adoption	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative impact of ASC 606 adoption	Accumulated Other Comprehensive Loss	Treasury Stock, at cost
Beginning Balance (in shares) at Jul. 31, 2017			41,728,934
Beginning Balance at Jul. 31, 2017	$ 523,932		$ 4,619	$ 174,602	$ 407,590		$ (9,900)	$ (52,979)
Increase (Decrease) in Stockholders' Equity
Repurchases of shares (in shares)			(62,559)
Repurchases of shares	(7,074)							(7,074)
Stock-based compensation	$ 9,615			9,615
Equity vests/option exercises (in shares)	52,500		46,551
Equity vests/option exercises			$ 5	(5)
Cancellations of restricted stock (in shares)			(6,842)
Dividends on common stock	$ (7,091)				(7,091)
Net income	$ 91,041				91,041
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Other comprehensive income (loss)	$ (1,556)						(1,556)
Ending Balance (in shares) at Jul. 31, 2018			41,706,084
Ending Balance at Jul. 31, 2018	608,867	$ 865	$ 4,624	184,212	491,540	$ 865	(11,456)	(60,053)
Increase (Decrease) in Stockholders' Equity
Repurchases of shares (in shares)			(43,734)
Repurchases of shares	(4,741)							(4,741)
Stock-based compensation	$ 15,562			15,562
Equity vests/option exercises (in shares)	30,000		67,862
Equity vests/option exercises	$ 950		$ 8	942
Issuance of shares (in shares)			42,703
Issuance of shares	3,210		$ 4	3,206
Cancellations of restricted stock (in shares)			(1,687)
Dividends on common stock	(8,350)				(8,350)
Net income	55,042				55,042
Other comprehensive income (loss)	(10,741)						(10,741)
Other	$ 873			873
Ending Balance (in shares) at Jul. 31, 2019	41,771,228		41,771,228
Ending Balance at Jul. 31, 2019	$ 661,537		$ 4,636	204,795	539,097		(22,197)	(64,794)
Increase (Decrease) in Stockholders' Equity
Repurchases of shares (in shares)			(497,217)
Repurchases of shares	(32,343)		$ (44)	(28,236)				(4,063)
Stock-based compensation	$ 12,076			12,076
Equity vests/option exercises (in shares)	25,000		137,914
Equity vests/option exercises	$ 919		$ 14	905
Issuance of shares (in shares)			751,471
Issuance of shares	54,391		$ 75	54,316
Cancellations of restricted stock (in shares)			(1,178)
Dividends on common stock	(4,471)				(4,471)
Net income	13,708				13,708
Equity component of convertible debt	29,184			29,184
Other comprehensive income (loss)	$ (5,402)						(5,402)
Ending Balance (in shares) at Jul. 31, 2020	42,162,218		42,162,218
Ending Balance at Jul. 31, 2020	$ 729,599		$ 4,681	$ 273,040	$ 548,334		$ (27,599)	$ (68,857)